The Drosophila alcohol dehydrogenase (Adh) gene encodes an enzyme which is necessary to detoxify alcohols encountered by the fly in its food sources. The gene is expressed at high levels in the larval and adult stages of development. This expression is restricted to specific tissues, chiefly the fat body, midgut, and Malpighian tubules. In addition, Adh transcription is temporally regulated: The gene has two different promotors which are active at different developmental times. The objective of this project is to identify and study the cis- and trans-acting genetic elements which are responsible for the regulated expression of Adh. Cis-acting sequences will be identified by introducing specific mutations in a cloned Adh gene in vitro and comparing the expression of mutant and wild-type genes in vivo following germline transformation. The regulatory properties of these elements will be further defined by studying their effect on the expression of heterologous genes in vivo using gene fusions. Trans-acting functions will be identified using two approaches. First, chemical selection techniques will be employed to screen for mutants in loci which regulate Adh expression in trans. Secondly, in collaboration with Dr. Robert Tjian, purified protein factors, defined in vitro by their specific interaction with cloned Adh DNA, will be used as the starting point for molecular cloning of the corresponding genes and an analysis of their developmental expression. The results of this project will advance our understanding of a fundamental problem of development in eukaryotes--the mechanisms by which a gene, present in all cells of an organism throughout its life, may be expressed only in specific tissues and at specific developmental times.